It is known in the market to furnish fuel cell systems, internal combustion engines, and other functional systems that generate heat in mobile or stationary use with cooling circuits in order to keep them at an optimal temperature range for ensuring their function. In the cooling circuits, preferably liquid cooling media (i.e., cooling fluids) are circulated, in particular cooling water or mixtures of cooling water and glycol. In the cooling circuits, there are compensation containers for the liquid cooling medium. In order to ensure optimal cooling and service life of all components of the cooling circuit and of the functional system, it is known to treat the cooling medium in the cooling circuit with appropriate additional treatment units. It is known to employ filters and/or ion exchangers in the cooling medium circuit with which the cooling medium in operation can be purified or freed of undesirable ions. In particular in fuel cell systems, it is necessary that the cooling fluid is desalinated because otherwise there is the risk of short-circuiting due to the conductivity of the cooling fluid.
The treatment units increase however the space that is required for the cooling device, in particular because they should be accessible easily for servicing purposes. These conditions are not easily fulfilled in particular in case of use in motor vehicles where there is only limited mounting space available. JP 2004311347 A1 discloses a cooling system for a fuel cell system in which at the lower end of the cooling fluid compensation container a treatment unit in the form of an ion exchanger is arranged.